Study of Compression-Induced Supramolecular Nanostructures
of an Imidazole Derivative
by Langmuir–Blodgett Technique

In
this communication, we report the design and synthesis as well
as the supramolecular assembly behavior of a 2,4,5-triaryl imidazole
derivative (compound <b>1</b>) at the air–water interface
and in thin films using Langmuir–Blodgett (LB) technique. The
main idea for such a chemical structure is that the long alkyl chain
and N–H of the imidazole core may help to form supramolecular
architecture through the hydrophobic–hydrophobic interaction
and hydrogen bonding, respectively. Accordingly, the interfacial behavior
as well as morphology of <b>1</b> in thin films were studied
through a series of characterization methods such as surface pressure–area
(π–<i>A</i>) isotherm, hysteresis analysis,
ultraviolet–visible (UV–vis) absorption and steady-state
fluorescence spectroscopies, Fourier transform infrared, X-ray diffraction,
Brewster angle microscopy (BAM), and atomic force microscopy (AFM)
measurements, and so forth. Pressure–area isotherm is an indication
toward the formation of supramolecular nanostructures instead of an
ideal monolayer at the air–water interface. This has been confirmed
by the hysteresis analysis and BAM measurement at the air–water
interface. AFM images of <b>1</b> in the LB monolayer exhibits
the formation of supramolecular nanowires as well as nanorods. By
controlling different film-forming parameters, it becomes possible
to manipulate these nanostructures. With the passage of time, the
nanowires come close to each other and become straight. Similarly,
nanorods come close to each other and form bundles of several rods
in the LB films. H-bonding, J-aggregation, as well as compression
during film formation might play a key role in the formation of such
nanostructures. Electrical switching behavior of compound <b>1</b> was also observed because of the presence of an electron donor–acceptor
system in <b>1</b>. This type of organic switching behavior
may be promising for next-generation organic electronics.